productivity area and decline both to the north and
south. The general model erected to explain the
Penrhyn Basin nodule variability thus probably applies, at least in part, to these areas also.
The model also has some applicability in the Indian Ocean but less in the Atlantic. In the Indian
Ocean, diagenetic nodules associated with sediments
containing moderate amounts of organic carbon
occur resting on siliceous ooze to the south of the
equatorial zone in the Central Indian Ocean Basin.
Farther to the south these nodules give way to hydrogenous varieties resting on pelagic clay. However,
in the north the changes in nodule composition that
might be expected under higher productivity waters
do not occur, probably because terrigenous sedimentation becomes important in those areas which
in turn reduces the Mn, Ni, and Cu content of
nodules. In the Atlantic, the influence of equatorial
high productivity on nodule composition that is
evident in the Pacific is not seen, mainly because the
seafloor in the equatorial area is largely above the
CCD. Where diagenetic nodules do occur, as in the
Angola, Cape and East Georgia Basins, productivity
is also elevated, but the seafloor is near or below the
CCD leading to reduced sedimentation rates.
Conclusions
Manganese nodules, although not being mined
today, are a considerable resource for the future.
They consist of ferromanganese oxides variably enriched in Ni, Cu, and other metals. They generally
accumulate around a nucleus and exhibit internal
layering on both a macro- and microscale. Growth
rates are generally slow. The most potentially economic varieties of the deposits occur in the subequatorial Pacific under the flanks of the equatorial
zone of high biological productivity, at depths near
the CCD. Similar nodules occur in the Indian Ocean
under similar conditions.
See also
Authigenic Deposits. Hydrothermal Vent Fluids,
Chemistry of.
Further Reading
Cronan DS (1980) Underwater Minerals. London:
Academic Press.
Cronan DS (1992) Marine Minerals in Exclusive Economic
Zones. London: Chapman and Hall.
Cronan DS (ed.) (2000) Handbook of Marine Mineral
Deposits. Boca Raton: CRC Press.
Cronan DS (2000) Origin of manganese nodule ‘ore
provinces’. Proceedings of the 31st International
Geological Congress, Rio de Janero, Brazil, August
2000.
Earney FC (1990) Marine Mineral Resources. London:
Routledge.
Glasby GP (ed.) (1977) Marine Manganese Deposits.
Amsterdam: Elsevier.
Halbach P, Friedrich G, and von Stackelberg U (eds.)
(1988) The Manganese Nodule Belt of the Pacific
Ocean. Stuttgart: Enke.
Nicholson K. Hein J, Buhn B, Dasgupta S (eds.) (1997)
Manganese
Mineralisation:
Geochemistry
and
Mineralogy of Terrestrial and Marine Deposits.
Geological Society Special Publication 119, London.
Roy S (1981) Manganese Deposits. London: Academic
Press.
Teleki PG, Dobson MR, Moore JR, and von Stackelberg U
(eds.) (1987) Marine Minerals: Advances in Research
and Resource Assessment. Dordrecht: D. Riedel.
MANGANESE NODULES 373
south. The general model erected to explain the
Penrhyn Basin nodule variability thus probably applies, at least in part, to these areas also.
The model also has some applicability in the Indian Ocean but less in the Atlantic. In the Indian
Ocean, diagenetic nodules associated with sediments
containing moderate amounts of organic carbon
occur resting on siliceous ooze to the south of the
equatorial zone in the Central Indian Ocean Basin.
Farther to the south these nodules give way to hydrogenous varieties resting on pelagic clay. However,
in the north the changes in nodule composition that
might be expected under higher productivity waters
do not occur, probably because terrigenous sedimentation becomes important in those areas which
in turn reduces the Mn, Ni, and Cu content of
nodules. In the Atlantic, the influence of equatorial
high productivity on nodule composition that is
evident in the Pacific is not seen, mainly because the
seafloor in the equatorial area is largely above the
CCD. Where diagenetic nodules do occur, as in the
Angola, Cape and East Georgia Basins, productivity
is also elevated, but the seafloor is near or below the
CCD leading to reduced sedimentation rates.
Conclusions
Manganese nodules, although not being mined
today, are a considerable resource for the future.
They consist of ferromanganese oxides variably enriched in Ni, Cu, and other metals. They generally
accumulate around a nucleus and exhibit internal
layering on both a macro- and microscale. Growth
rates are generally slow. The most potentially economic varieties of the deposits occur in the subequatorial Pacific under the flanks of the equatorial
zone of high biological productivity, at depths near
the CCD. Similar nodules occur in the Indian Ocean
under similar conditions.
See also
Authigenic Deposits. Hydrothermal Vent Fluids,
Chemistry of.
Further Reading
Cronan DS (1980) Underwater Minerals. London:
Academic Press.
Cronan DS (1992) Marine Minerals in Exclusive Economic
Zones. London: Chapman and Hall.
Cronan DS (ed.) (2000) Handbook of Marine Mineral
Deposits. Boca Raton: CRC Press.
Cronan DS (2000) Origin of manganese nodule ‘ore
provinces’. Proceedings of the 31st International
Geological Congress, Rio de Janero, Brazil, August
2000.
Earney FC (1990) Marine Mineral Resources. London:
Routledge.
Glasby GP (ed.) (1977) Marine Manganese Deposits.
Amsterdam: Elsevier.
Halbach P, Friedrich G, and von Stackelberg U (eds.)
(1988) The Manganese Nodule Belt of the Pacific
Ocean. Stuttgart: Enke.
Nicholson K. Hein J, Buhn B, Dasgupta S (eds.) (1997)
Manganese
Mineralisation:
Geochemistry
and
Mineralogy of Terrestrial and Marine Deposits.
Geological Society Special Publication 119, London.
Roy S (1981) Manganese Deposits. London: Academic
Press.
Teleki PG, Dobson MR, Moore JR, and von Stackelberg U
(eds.) (1987) Marine Minerals: Advances in Research
and Resource Assessment. Dordrecht: D. Riedel.
MANGANESE NODULES 373